This invention relates generally to aircraft engines and more particularly to mounts for supporting an engine on an aircraft.
An aircraft engine may be mounted to an aircraft at various locations such as the wings, fuselage or tail. The engine is typically mounted at both its forward and aft ends by corresponding forward and aft mounts for carrying various loads to the aircraft. The loads typically include vertical loads such as the weight of the engine itself, axial loads due to the thrust generated by the engine, lateral loads such as those due to wind buffeting, and roll loads or moments due to rotary operation of the engine. The mounts must also accommodate both axial and radial thermal expansion and contraction of the engine relative to the supporting pylon.
One exemplary mount includes a pair of circumferentially spaced apart prime links mount includes a pair of circumferentially spaced apart prime links. Each prime link is joined at one end to the aircraft and at the other end to a casing in the engine. At least one of the prime links is fixedly joined to the aircraft by two pins such that the link will not rotate in a plane extending perpendicularly through the centerline axis of the engine. This fixed prime link is provided so that the mount can accommodate in-plane loads, i.e. those in a single vertical axial plane extending perpendicularly to the engine centerline axis, including the vertical loads, lateral or horizontal loads, and roll loads or moments. By rigidly joining the fixed prime link to the aircraft at two points and to the engine casing at a single point, the fixed prime link can transfer in-plane loads from the engine to the aircraft through tension, compression, and bending thereof.
The other prime link can be pivotally joined between the aircraft and engine casing so as to only transfer tensile and compressive loads along its longitudinal axis. This so-called swing link is otherwise free to rotate in-plane relative to the aircraft and engine casing. Allowing the swing link to rotate accommodates radial expansion and contraction of the engine without introducing additional reaction stresses that would otherwise occur.
This exemplary mount further includes a waiting failsafe link disposed between the two prime links. The failsafe link is normally not a load bearing member, but is provided solely for carrying loads upon failure of either one of the prime links. The failsafe link is joined at one end to the aircraft and at the other end to the engine casing, typically via clearance pin joints in which pins extend through holes formed in the ends of the failsafe link and a corresponding clevis formed on the supporting structure. One of these joints is provided with a predetermined clearance between the pin and the hole so that during normal operation of the mount, no loads are transferred from the engine to the aircraft through the failsafe link. However, upon failure of either prime link, the pin will contact the failsafe link at its hole for transferring loads through the failsafe link that would otherwise be transmitted through the failed prime link.
Although generally operating in a satisfactory manner, this exemplary mount suffers from a potential drawback in that the clearance required in the connection joints of the failsafe link typically results in loose pieces that vibrate and cause wear or other damage. Furthermore, the joints that connect the prime links to the aircraft typically require costly precision machining to avoid assembly stack-up issues that would impede installation of the engine. Conventional prime link joints can also result in undesirable thermal stresses.
Accordingly, there is a need for an aircraft engine mount that avoids the wear and thermal stress problems of conventional mounts while being relatively easy to assemble.